This invention relates generally to weighing scales, and more particularly to multiple load element scales where the load elements are attached to the scale platform.
It is common practice to utilize multiple load cells on a weighing scale. One well-known type of such scale takes the form of four load cells, one at each corner of a rectangular scale, with load cells rigidly attached to a rigid base on one side, and to a rigid platform on the other. A weight placed on the weighing platform is supported by the four load cells. The electrical output from the load cells may be properly summed electrically to provide an output voltage which is proportional to the weight applied on the platform.
Great care must be taken that only vertical forces are measured. Horizontal forces are introduced by many factors including: misalignment between the top platform and bottom base structures; thermal expansion and compression of the load cells, mounting structures, and base and platform structures; and misalignment of the load cells' bearing axis such that the load cells' bearing axis is not aligned in a perfectly perpendicular manner with the platform.
It is common practice to decouple these horizontal forces by means of complex flexures machined into the load cells in combination with single-point pivots, ball bearings and cups, and similar means which will only support vertical forces. As is well appreciated in the art, such means are difficult and expensive to implement.